Camera modules for use in vehicles generally include an objective mount (lens holder), an image sensor (imager chip), and an objective held in the objective mount. The optical axis of the camera module is determined by the image sensor and the objective. The objective mount includes a generally cylindrical or tubular wall region, into which the objective is placed; the objective generally includes a lens holder and one or more lenses held by the lens holder. The objective mount may be used as a circuit substrate, so that the image sensor may be mounted directly to the objective mount; as an alternative to this, the objective mount may also be attached to a circuit substrate, on which the image sensor is mounted.
In the assembly of such camera modules, the reliable and rapid mounting of the objective in the objective mount is important for a high throughput and a high yield, that is, low defect rates. In this connection, it is advantageous when the positioning of the objective, which is ascertained via a sharpness test, may ultimately be set directly in the adjusting device without, for example, displacement being able to occur during the curing process of an adhesive.
To this end, it is known that in general, the objective may be introduced into the objective mount in a linear motion. This may be accomplished, first of all, using a screw thread; however, alignment with the aid of such a thread may normally not be carried out in a highly precise manner, since the thread must always be designed to have play, in order to prevent seizing or blocking of the thread during focusing. On the other hand, the play may result in displacement of the objective during a subsequent machining step, and may therefore cause a loss of sharpness. In addition, screwing operations are more time-consuming than purely linear motions.
However, when the objective is moved linearly into the objective mount, abrasion between the objective mount and the lens holder may occur, which may result in a build-up of particles on the image sensor and may therefore markedly reduce the quality of the image.
German Published Patent Application No. 10 2006 000 641 A1 describes the securing of an objective in an objective mount, in which the clamping ring is placed externally around the objective mount and is biased by reducing its diameter. However, instances of such large biasing may permanently deform the objective mount, for example, and therefore cause defocusing. In addition, shavings, which fall onto the image sensor and consequently affect the image quality, may also be formed while inserting the objective into the objective mount.
German Published Patent Application No. 10 2007 029 475 A1 describes the holding of a lens in the lens holder via a positive fit between the lens surface and the inner surface of the lens holder; the positive fit may be achieved by a groove on one of the components and a projection or lip on the other component.